The present invention relates to a portion capsule for producing a beverage, having a capsule body with a capsule base and a filling side, with a cavity for accommodating a pulverulent or liquid beverage base being formed between the capsule base and the filling side, and with a filter element being arranged between the beverage base and the capsule base.
Portion capsules of this kind are generally known from the prior art. By way of example, documents EP 1792850 B1, EP 1344722 A1 and US 2003/0172813 A1 disclose portion capsules of this generic type for preparing coffee and espresso.
Portion capsules of this kind for producing a beverage are preferably in the form of a truncated cone or cylinder and are produced, for example, from a thermoformed plastic film or using a plastic injection molding process. Said portion capsules usually have an open filling side with a collar edge onto which a cover film or foil is sealed or adhesively bonded, a closed capsule base, with a particle screen which is supported against the capsule base being arranged between the beverage base and the capsule base. These screens are either injection molded from a thermoplastic or are thermoformed or stamped from a plastic film.
For the purpose of preparing a coffee beverage, the portion capsule is inserted into a brewing chamber of a preparation appliance. After or during the closing process of the brewing chamber, the capsule is preferably opened on its closed base side by means of an opening mandrel which is arranged in the brewing chamber and, after the brewing chamber is sealed off, the filling side of the portion capsule, which filling side is sealed off by a sealing film or foil, is tapped by means of a puncturing means. Preparation liquid, preferably hot water, is then delivered into the portion capsule under pressure. The preparation liquid flows through the beverage base and extracts and/or dissolves the substances, which are required for producing the beverage, from the beverage base. For the purpose of preparing an espresso, for example a brewing water pressure of up to 20 bar acts on the coffee powder for the purpose of extracting the essential oils. This pressure also acts on the particle screen which is situated between the coffee powder and the capsule base and in front of the punctured capsule outlet.
A disadvantage of the screens which are produced using a plastic injection molding process or using a thermoforming or stamping process is, however, that the openings in the screen holes have to be smaller than the smallest coffee particles in order to retain the coffee particles. Since a certain proportion of dust is necessarily produced in a coffee grinding process, coffee particles pass through if the screen holes are too big or the screens are blocked if the screen holes are too small, in particular at high pressures. Furthermore, corresponding supporting elements which act against the capsule base are required beneath the screens in order to absorb the brewing water pressures of up to 20 bar and to prevent deformation of the screens as a result of the high brewing water pressure (together with a high brewing water temperature). These supporting elements disadvantageously require additional material to be used, particularly in the case of screen arrangements produced using an injection molding process, as a result of which the production costs rise.
Therefore, the prior art discloses portion capsules with screen arrangements which are intended to avoid these disadvantages. U.S. Pat. No. 2,778,739, EP 1710173 A1 and U.S. Pat. No. 5,325,765 disclose portion capsules having screen arrangements which consist of a screen support with relatively large passage openings, with these openings being covered by a filter material. A disadvantage of these arrangements is that additional costs for material and manufacture are incurred for forming such screen arrangements since they consist of a stable screen support and the filter material which is arranged on the screen support.
Both in the case of screens with screen holes and in the case of screen arrangements with an additional filter material, it is necessary to ensure that the ready beverage which passes through the screen arrangement can flow to a capsule outflow opening, that is to say a free space for the discharge of a beverage has to be provided between the capsule base and the screen arrangement. In addition, screen arrangements of this kind take up their own proportion of space in the portion capsule, this leading to an increase in the volume of the capsule and thus necessarily likewise to additional material being used.
The object of the present invention was therefore to provide a portion capsule having a filter arrangement, which portion capsule is less expensive to manufacture in comparison to the prior art and in which the disadvantages described in connection with the prior art are avoided at the same time.